A. Field of Invention
The present application pertains to a method and apparatus for guiding an ablation catheter automatically using cardiac signals sensed in real time.
B. Description of the Prior Art
Catheter ablation is a surgical technique used for treating patients with cardiac arrhythmia (such as supraventricular tachycardia or SVT) or other illnesses when the patient does not respond to medicine. The procedure involves interrupting or otherwise altering electrical pathways in the heart by applying energy to specific pathological cardiac tissues.
Currently available cardiac catheters are used to apply thermal, RF, or cryogenic energy to perform ablation. Typically, these catheters are fairly complex and include guiding elements for guiding the distal aspect or end of the catheter, sensor electrodes for sensing intrinsic electrical pathways or conductive tissue in the heart, as well as active electrodes that provide the actual energy for the procedure once the desired cardiac tissue is reached.
The distal end of the catheter can be manipulated and modified by an operator using manual controls to position it in contact with diseased cardiac tissue for delivery of ablative energy for cauterizing abnormal conductive tissue. Catheters of a variety of catheter shapes and sizes are available from numerous manufacturers (such as Boston Scientific, Medtronic, and Biosense Webster) and many catheters are designed to be deformable using mechanisms incorporated onto a hand held controller with triggers, knobs or collars as are understood in the art.
However, such catheters are limited in their ability to detect and localize electrical pathways that are aberrant and often require prolonged attempts by the operator for proper positioning thereof for the procedure to be successful. This prolonged process increases the risk of complications and duration of radiation exposure.
Medical catheters and sheaths are generally tubular shaped and of a sufficiently small diameter to be inserted into a patient's body through a small incision, puncture or a natural opening. Such catheters can include mechanisms to deploy inner catheters, cardiac leads, electrodes, deliver contrast (e.g. radiopaque dye) or ablative energy (e.g. current, radiofrequency energy, light, ultrasound), and are often flexible.
By way of example, a catheter capable of delivering electrical energy has been developed by Diaz et. al. (U.S. Pat. No. 5,836,946). This catheter allows for transmitted electrical energy along an outer layer of stranded conductive fibers that delivers electrical energy through a cutting tip for multipolar electro-cautery. Wells (U.S. Pat. No. 4,844,062) describes a rotating fiber optic laser catheter assembly with an eccentric lumen that provides for the ablation of obstruction in vessels such as coronary arteries via transmitted laser energy. Taylor et al (U.S. Pat. No. 5,484,433) patented a deflectable tissue-ablating device that uses a plurality of optical fibers for delivery of light energy. Hammersmark et al. (U.S. Pat. No. 5,429,604) developed a fiber optic catheter with a twistable tip. Such technology is implemented for accessing various anatomic locations such as about the pulmonary veins, atria-ventricular node, and accessory pathways. Cardiac and vascular perforations are complications associated with these procedures.
Mechanisms for deflecting catheters are well known in the art (e.g. Lennox, et al. U.S. Pat. No. 5,571,088). More particularly, designs for controlled deflection of the distal aspect of the catheter shaft are known using a pull-wire that extends from a handle at the proximal end of the catheter through a lumen in catheter shaft and is fastened to distal end of the catheter shaft. Such a design is constructed such that the distal end is more flexible then the proximal segment. In this fashion, when the handle is pulled back the pull wire causes distal end to bend preferentially from an un-deflected position to a deflected position. The distal tip of the catheter shaft can be brought into contact with a wall of heart by controllably deflecting the distal end of the catheter. The electrode senses electrical potentials within the heart for the purpose of locating cardiac tissue containing abnormal electrical pathways and the operator can apply radiofrequency current to the electrode at distal tip for ablation of localized cardiac tissue. This mechanism does not ensure tissue contact nor does it serve to anatomically locate the treating portion of the distal member into the proper location for delivery of therapy.
Thus, there is a need for a method to optimize the location of the catheter's distal end where therapy is delivered to pathologic tissue, and an apparatus for performing the method.